No load speed is depended up on the synchronous speed (Ns) where Ns = 120f / p where p = no of poles f = supply frequency hence the answer is d

The correct answer is option 'B' - the number of poles. Let's understand why.

No-load speed of an induction motor refers to the speed at which the motor operates when there is no mechanical load connected to its shaft. It is the speed at which the motor rotates when no external torque is applied.

There are several factors that affect the no-load speed of an induction motor, such as the supply frequency, the number of poles, and the maximum flux per phase. However, only option 'B' - the number of poles - is directly related to the no-load speed.

Here's why the number of poles affects the no-load speed of an induction motor:

1. Introduction to poles:
- In an induction motor, the stator contains a set of windings that create a rotating magnetic field when supplied with three-phase AC power.
- The number of poles refers to the number of magnetic poles created by these windings in the stator.

2. Relationship between speed and number of poles:
- The no-load speed of an induction motor is inversely proportional to the number of poles.
- This means that as the number of poles increases, the no-load speed decreases, and vice versa.
- For example, a motor with four poles will have a lower no-load speed compared to a motor with two poles.

3. Explanation:
- The rotating magnetic field created by the stator windings induces currents in the rotor, which in turn creates a magnetic field in the rotor.
- The interaction between the stator and rotor magnetic fields causes the rotor to rotate.
- The speed of rotation is determined by the synchronous speed, which is directly related to the supply frequency and the number of poles.
- The synchronous speed is given by the formula: Synchronous Speed (in RPM) = (120 * Frequency) / Number of Poles.
- As the number of poles increases, the synchronous speed decreases.
- The actual speed of the motor, including the slip (difference between synchronous speed and actual speed), is slightly lower than the synchronous speed.
- Therefore, the no-load speed of an induction motor is directly influenced by the number of poles.

In conclusion, the correct answer is option 'B' - the number of poles. The no-load speed of an induction motor depends on the number of magnetic poles created by the stator windings. As the number of poles increases, the no-load speed decreases.